1. Field of the Invention
The present invention relates to a camera with an autofocus system. In particular, it relates to a camera with an autofocus system using a contrast detection method.
2. Description of the Related Art
In a digital camera such as a compact type digital camera, an autofocus system utilizing a contrast detection method is incorporated in a camera as a servomechanism. In the contrast detection method, contrast data are successively detected on the basis of image-pixel signals read from an image sensor, and auto-focusing is performed. When peak or maximum contrast data is detected, in other words, when high spatial high frequency components in an object image becomes a highest value, it is determined that an object is in focus, and a focusing lens is driven to the focused point. The user can confirm the focused situation via an LCD monitor on a rear surface of the camera.
Usually, the focused position is detected by a gradient method (the so called “climbing method”) in which a top point in a distributed curved line of high frequency components is searched. The contrast data is successively detected while continuously driving a focusing lens, and it is determined that an object is in focus when the contrast data has a peak value.
To confirm whether the contrast data is actually a peak contrast data, the focusing lens is driven so as to surpass the focused position, and a plurality of contrast data are further detected, causing it to be difficult to shorten the required time for focusing.